Irregular Source Geometries for Ios Pele Plume William McDoniel David Goldstein Philip Varghese Laurence Trafton The University of Texas at Austin 42 nd DPS Meeting October 6 ID: 618237
Download Presentation The PPT/PDF document "DSMC Simulations of" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
DSMC Simulations of Irregular Source Geometries for Io’s Pele Plume
William McDonielDavid Goldstein, Philip Varghese, Laurence Trafton
The University of Texas at Austin
42
nd
DPS Meeting
October 6
th
, 2010
Supported by the NASA Planetary Atmospheres ProgramSlide2
Pele
Canopy rises to over 300km
Deposition ring is ~1200km acrossTemperatures in excess of 1000K observed via IR
Ring changes over time, but remains ovoid
10km
120kmSlide3
Source Geometries
Previous plume simulations used only round vents.Irregularities in Pele’s structure likely caused by unsteadiness or source geometry.
Steady irregularities due to source geometry, and this must be simulated
Observational clues to the actual source:
-consistently ovoid ring
-black “butterfly wings”
-Galileo IR image of part of Pele’s caldera
-Galileo/Voyager images of the calderaSlide4
Basic DSMC Overview
Simulates gas dynamics using a “large” number of representative particlesParticle collisions and movement are de-coupled in a given timestepBinary collisions between particles in the same cellParticles move using F=maSlide5
Plume Simulations
Earlier axisymmetric simulations of Pele using DSMC.The plume expands, collapses back on itself, and forms a large canopy.The gas can bounce off of the surface, and form secondary rings, depending on surface temperature.Slide6
Cold Line Source
Vent number density:
5 × 10
18
m
-3
(under-resolved)
240km
1200km
10kmSlide7
Hot Line Source
Focusing at hot conditions – 650K and 900m/s at the vent. Near-field number density contours at ground level and along the dashed line.
Focusing is more pronounced than with cold cases. Four orders of magnitude difference between red jets and blue expansion regions.
13km
20km
A
A’
A’
ASlide8
Cold Lava Lake
Vent number density:
~2 × 10
16
m
-3
.
Orientation is almost exact.
120km
240km
1200kmSlide9
Cold Lava Lake
A’
A
A
A’
B
B’
B
B’
Number density contours through the plume along two planes.
240km
240kmSlide10
Other Sources?Slide11
Conclusions
DSMC can provide insight into the source geometry of Ionian plumes.A curved line source, as seen in the Galileo IR image, can produce the features seen in observations of Pele’s deposition pattern.
But
the observed hot line
cannot
be the only source of plume material because it produces a ring with a different orientation.
Gas must be produced elsewhere in the caldera, perhaps in a line across the top of the lava lake.